In order to cope with positively natural disasters, such as earthquake and tsunami, it is necessary to establish an earthquake and tsunami warning system, i.e., an ETWS. When the natural disasters, such as earthquake and tsunami, occur, information regarding to the disasters may be sent to users timely through this system, thereby mitigating the influence of the natural disasters, such as earthquake and tsunami, on human.
FIG. 1 is a structure diagram of a network in which an operator of a public land mobile network (PLMN) provides earthquake and tsunami warning services for users through an ETWS. When disaster events will soon occur or after they occur, the government or other organs issue a warning notification to the operator of the PLMN, who sends a warning notification message to the masses of users through the ETWS included in the box in the figure.
According to differences of emergency degrees and purposes, the warning notification message may be divided into two types: the first type of notification message is known as a primary notification message which contains the most important disaster information (e.g., the earthquake or tsunami will soon occur) and is required to be transmitted to the users by the system in 4 s; the second type of notification message is known as a secondary notification message which contains auxiliary information regarding to the disasters (e.g., where assistance can be obtained) and is required to be transmitted to the users by the system in 10 s to 30 s. The primary notification message is composed of two portions: basic information and security information, where the basic information contains contents, such as warning type, warning area, etc., and has a length of 5 bytes; and the security information provides digital signature and time stamp for the basic information and has a length of about 50 bytes.
A system architecture of an ETWS in a LTE system proposed in the prior art is as shown in FIG. 2. The ETWS is implemented using a cell broadcast center (CBC), and the network architecture and interfaces of the ETWS are as shown in FIG. 2. The ETWS is comprised of an evolved universal terrestrial radio access network (E-UTRAN), a mobility management entity (MME), a serving gateway (S-GW), a packet data network gateway (P-GW), a home subscriber server (HSS), a policy and charging rule function (PCRF) entity and other supporting nodes. Based on the network architecture, when a base station in the E-UTRAN, which also called as an evolved node B, i.e., eNB, sends the primary notification message of the ETWS to a terminal, also called as user equipment (UE), via an air interface Uu, if a way of paging the UE first and then sending the primary notification message of the ETWS to the terminal through a system message in the next system message modification period (which typically will exceed 5 s) is applied, the time delay requirement of 4 s for the primary notification message will not be satisfied.